The present invention relates to an electronic assembly having high-density interconnections. A particular application of the invention lies in the field of integrated electronic modules, i.e. modules comprising a plurality of specialized integrated circuits known as application specific integrated circuits (ASICs). These ASICs perform numerous complex functions, and for them to operate it is necessary for a large number of inlet and outlet ports on the module to be served. The field of the invention is particularly that of integrated modules of three-dimensional structure, and in a preferred example, in the form of a cube.
In the state of the art, cube-shaped integrated electronic modules are known that are connected via one of their faces to a printed circuit card. The electronic module is mounted by soldering tabs on the module to transfer contacts on the card. In order to dissipate the heat given off by such a module in operation, a heat removal system is known including a heat drain, which heat drain is embedded in the card. The module has a face that is placed on or in register with a zone of the printed circuit card. This face is the only interface between the module and the card. Thus, the functions of interconnection and of removing heat are both performed via said interface.
The state of the art assembly raises a problem since it firstly prevents the module from providing interconnections at high density. Secondly, the heat removal system that is provided is not sufficient since it is made in the printed circuit card, even through firstly the amount of heat to be removed is large and secondly the removal system cannot be too large in size given the miniaturization conditions imposed on such integrated modules and printed circuit cards. Furthermore, the card cannot receive a miniature heat removal system of higher performance since it is constituted by a substrate made of a material that has poor heat conduction characteristics.
An object of the invention is to remedy the above-mentioned problem by proposing an electronic assembly provided with a cooling device and also proposing interconnection means for the electronic module, the interconnection means being distinct from the cooling device. The advantage of the invention is to make use of the three-dimensional structure of the electronic module to separate the interconnection function and the heat removal function, thereby enabling each of these functions to be optimized independently of the other.
The cooling device of the invention consists in an insulating soleplate connected to one of the faces of the integrated module, said face being distinct from a second face of said module, the second face being presented in such a manner as to be suitable for connection with a printed circuit card. The soleplate is selected to have good heat exchange capacity. Since it presents no interconnection function for the module, it can act without interference to remove the large quantity of heat emitted by the module.
In addition, the entire second face of the module can be used for providing interconnection functions, and none of its area needs to be set aside for removing heat. Consequently, the invention makes it possible to propose a module that offers a greater density of interconnections.
The invention provides an electronic assembly comprising at least a first integrated electronic module, the first module including at least one interconnection means for optical connection to a printed circuit card or to a second electronic module, the assembly including a soleplate and heat removal means for removing heat from said module to the soleplate, and wherein the soleplate is independent of the interconnection means of the first module.
In the state of the art, modules are known that are provided with optical interconnection means. Optical interconnection means present the advantage of being insensitive to the electromagnetic fields created in environments of the kind that surround modules of the invention. In addition, optical interconnections present the advantage of making it possible to achieve a greater density of interconnections than when using electronic interconnections.
In the state of the art, optical interconnection means comprise an optical fiber and an optical connector unit. The connector unit has a first optical connector mounted on the module, for example, and a second optical connector mounted on one end of the optical fiber for connecting the optical fiber to the module. The first and second connectors need to be assembled together with very great precision. The end of the optical fiber must be put into register with the first optical connector very precisely in order to guarantee good transmission of the optical signal through the connector unit. For this purpose, the connector unit has at least one means for aligning the fiber with the first optical connector.
In general, the alignment means comprise specific transfer means. In general, the alignment means further comprise converging lenses to focus a light beam conveyed by means of such a fiber.
These optical interconnections and contacts present a major drawback. They are complex and bulky, and they are not suitable for designing modules having a high density of connections operating at high data rates. The first specific transfer means are bulky and prevent optical interconnections achieving high density on such miniature modules. Furthermore, proper positioning of the converging lenses is difficult to achieve. Finally, these extremely accurate alignment means are expensive, making the use of optical interconnections on integrated electronic modules expensive.
Another object of the invention is to remedy the problems mentioned by proposing a module having optical interconnection means that make it possible to avoid the presence of specific transfer means to guarantee the alignment accuracy that is required for such optical interconnections. The optical interconnection means of the invention no longer require the presence of a connector unit. The invention provides for an optical fiber, e.g. included in a printed circuit, to be put into register with an optical contact of the module merely by mounting the printed circuit with precision on a face of the module that has the optical contact. The precision mounting implemented is compact since the contact points between the printed circuit and the face are limited to micropoints that are disposed very accurately respectively on the face of the module and on the printed circuit. Thereafter, these micropoints are interconnected by capillarity during a step of melting the micropoints when they are at a very small distance apart from one another.
This method of bringing points into register thus enable the density of the optical connectors presented by such an electronic module to be increased because the space required for the specific transfer means of the optical connectors is now available to present additional optical contacts.
In a preferred example, the invention provides an electronic assembly comprising at least a first integrated electronic module, a printed circuit card, and optical interconnection means for connecting the integrated electronic modules to the printed circuit card, wherein the optical interconnection means comprise a first optical contact of the first integrated electronic module, and a second optical contact on the printed circuit card, and wherein the first optical contact is mounted precisely in register with the second optical contact by means of beads bonded to the module, the beads being self-centering with metal areas of the printed circuit card during assembly.